Organic nitriles such as Acetonitrile and Hydrogen Cyanide (HCN) are important building block in organic synthesis, and furthermore is used in the production of acrylic fibers and acrylonitrile-butadiene-styrene resins to make plastic moldings for a wide variety of applications. ACN is conventionally produced as a by-product from the acrylonitrile process, so that production trends for acetonitrile follow those of acrylonitrile. Recently this has led to a shortage of ACN.
A few methods for producing ACN as a direct product have been proposed. These processes require handling ammonia as a feed gas and have undesirable by-products.
U.S. Pat. No. 3,725,457 discloses the preparation of ACN by ammoxidation of acrolein, whereby increasing the amount of ammonia gas to this process results in a 2- to 10-fold yield increase. Yields of 42% ACN were reported.
U.S. Pat. No. 3,925,447 discloses preparation of hydrocarbon nitriles (but not ACN specifically) using ammonia gas and supported metal oxides having metal concentration in the range of 25 wt % to 75 wt %. According to this process, oxygen free conditions are required to produce nitriles with short contact times.
More recently, European patent publication EP0206632(A1) has described attempts to prepare ACN using ammonia gas and ethanol over a molybdenum catalyst on a silica support. ACN was prepared by reaction of ethanol and ammonia in a 1:4 mole ratio at optimum temperatures of about 400° C. This process uses a 12-molybdophosphoric acid catalyst on a high surface area silica gel support; a surface area of 500 m2/g is required to obtain the reported yield. The resulting product distribution gave 62% yield of acetonitrile with 4% unreacted ethanol, 12% ethylamine and 22%, 2-, and 4-picoline by-products formed through cracking side reactions.
There remains a need for a high-yield ACN production process that does not use acrylonitrile, avoids side reactions and by-products, and also avoids the dangers in handling ammonia gas.